The subject matter disclosed herein relates to elevator systems. More specifically, the subject matter disclosed herein relates to mitigation of sway of suspension and/or driving ropes for elevator systems.
Elevator systems typically include one or more ropes or other suspension members from which an elevator car is suspended, and with which the elevator car is driven along a hoistway. Tall buildings in particular, which have elevator systems servicing them, have some sway associated with them. This sway, most often experienced during periods of high winds, can seriously impact elevator performance and, in some instances, damage elevator components. For example, building sway can result in rope sway that, especially when the rope length is shortened as the car runs into an upper or lower landing, has a significant lateral amplitude that causes excessive vertical vibration and noise at the elevator car. Further, rope sway effects experienced at the elevator car are increased at certain floors where the rope sway frequency is at or near the building sway vibratory frequency.
The typical approach to rope sway mitigation involves deploying mechanical elements such as sway arms, snubbing devices, car followers, rope guides, isolators or the like. The mechanical elements such as the above increase system cost and many times lack the reliability necessary to prevent the effects of rope sway. Another solution includes adjusting a tie down sheave in the hoistway to minimize the effect of compensation rope sway during the high wind event. The building is then monitored for sway and wind modes are implemented limiting elevator performance, for example, stopping service to floors in a predetermined “critical zone”, at which the effects of the building sway on the elevator car are greatest. This approach, however, results in having many unserviceable floors of the building during building sway events, which is unacceptable to many elevator system users.